Stabilized thermoplastic moulding materials

ABSTRACT

Thermoplastic molding compositions comprising, based on the components A) to F),  
     A) from 5 to 70% by weight of at least one graft copolymer A) made from an elastomeric graft base with a glass transition temperature below 0° C., and a graft made from a styrene compound, and acryonitrile or methacrylonitrile or a mixture of these and, where appropriate, further monoethylenically unsaturated monomers,  
     B) from 29 to 90% by weight of a hard copolymer made from at least one styrene compound, acrylonitrile or methacrylonitrile or a mixture of these and, where appropriate, further monoethylenically unsaturated monomers,  
     C) from 0 to 5% by weight of at least one three-block copolymer X-Y-X having a central block Y made from propylene oxide units and having terminal blocks X made from ethylene oxide units,  
     D) from 0.01 to 5% by weight of at least one butylated reaction product of p-cresol with dicyclopentadiene,  
     E) from 0.01 to 5% by weight of at least one thiocarboxylic ester,  
     F) from 0.01 to 5% by weight of at least one alkali metal salt or alkaline earth metal salt of a C 6 -C 20  carboxylic acid, and  
     G) from 0 to 30% by weight, based on components A) to G), of other conventional additives, 
     where the weathered db* value of the molding compositions is below +5.0 after 100 hours of exposure to light and weathering to ISO 4892/2, method A, black-panel temperature 65° C., using the CIE-Lab color system, to DIN 6174 and DIN 5033.

[0001] The invention relates to thermoplastic molding compositionscomprising, based on components A) to F),

[0002] A) from 5 to 70% by weight of at least one graft copolymer A)made from, based on A),

[0003] a1) from 10 to 90 % by weight of at least one elastomeric graftbase with a glass transition temperature below 0° C., and

[0004] b2) from 10 to 90% by weight of at least one graft made from,based on a2),

[0005] a21)from 50 to 100% by weight of at least one styrene compound,

[0006] a22)from 0 to 50% by weight of acrylonitrile ormethacrylonitrile, or a mixture of these, and

[0007] a23)from 0 to 50% by weight of at least one othermonoethylenically unsaturated monomer,

[0008] B) from 29 to 90% by weight of a hard copolymer made from, basedon B),

[0009] b1) from 50 to 100% by weight of at least one styrene compound,

[0010] b2) from 0 to 50% by weight of acrylonitrile ormethacrylonitrile, or a mixture of these, and

[0011] b3) from 0 to 50% by weight of at least one othermonoethylenically unsaturated monomer,

[0012] C) from 0 to 5% by weight of at least one three-block copolymerX-Y-X having a central block Y made from propylene oxide units andhaving terminal blocks X made from ethylene oxide units,

[0013] D) from 0.01 to 5% by weight of at least one butylated reactionproduct of p-cresol with dicyclopentadiene of the formula (I)

[0014]  where n≦10,

[0015] E) from 0.01 to 5% by weight of at least one thiocarboxylicester,

[0016] F) from 0.01 to 5% by weight of at least one alkali metal salt,or alkaline earth metal salt, of a C₆-C₂₀ carboxylic acid, and

[0017] G) from 0 to 30% by weight, based on components A) to G), ofother conventional additives,

[0018] where the weathered db* value of the molding compositions isbelow +5.0 after 100 hours of exposure to light and weathering to ISO4892/2, method A, black-panel temperature 65° C., using the CIE-Labcolor system, to DIN 6174 and DIN 5033.

[0019] The invention also relates to processes for preparing the moldingcompositions, and to the use of the molding compositions for preparingmoldings, fibers and films, and also to the moldings, fibers and films.

[0020] Impact-modified styrene-acrylonitrile polymers, such as ABS(polybutadiene rubber particles grafted with polystyrene-acrylonitrile,in a polystyrene-acrylonitrile matrix) or ASA (polyalkyl acrylaterubber, structure otherwise as ABS) are used in a wide variety ofapplications. They are preferably used to produce moldings intended tohave good mechanical properties. It is often necessary to use additivesto give the molding compositions certain properties, such as antistaticproperties, and in particular good weathering resistance, etc.

[0021] French Patent 1 239 902 discloses thermoplastic moldingcompositions comprising an antistatic, EO-PO-EO three-block copolymers(EO is ethylene oxide, and PO is propylene oxide).

[0022] EP-A 135 801 describes blends made from polycarbonate, from ABSor ASA and from an EO-PO-EO three-block copolymer, with certain molarmasses for individual blocks.

[0023] EP-A 536 483 discloses ABS molding compositions which comprise aPO polymer whose ends have been capped with EO and which contains1,4-butylene terephthalate units.

[0024] U.S. Pat. No. 5,346,959 describes blends made from ABS, fromstyrene-maleic anhydride copolymer, and from OH-functionalized PO-EO-POblock copolymers (i.e. an EO central block).

[0025] DE-OS 16 940 101 describes ABS molding compositions stabilizedwith a phenolic stabilizer, with dilauryl thiodipropionate, and withC₁-C₂₀ fatty esters (butyl stearate).

[0026] British Patent 1 369 589 disclosesstyrene-butadiene-acrylonitrile copolymers which comprise phenolicstabilizers and dilauryl thiodipropionate, besides asbestos fibers.

[0027] EP-A 184 788 discloses flame-retardant ABS molding compositionswhich comprise stearically hindered phenols and costabilizers.

[0028] WO-A 95/02639 describes the stabilization of recycledstyrene-containing plastic from waste and collection of usefulmaterials. The stabilizers used comprise stearically hindered phenols,metal oxides/metal hydroxides/metal carbonates, esters ofthiodipropionic acid, and, if desired, metal salts of fatty acids.

[0029] WO-A 94/07951 discloses the stabilization of plastics from waste,using a mixture made from a stearically hindered phenol, from an organicphosphite or phosphonite, and from metal oxides/metal hydroxides/metalcarbonates.

[0030] EP-A 506 614 describes the stabilization of recycledthermoplastics using stearically hindered phenols and phosphoric esters.

[0031] EP-A 669 367 describes ABS molding compositions stabilized with atrialkyl phenol, with a stearically hindered phenol, and, if desired,with dilauryl or distearyl thiodipropionate.

[0032] EP-A 712 894 discloses ABS molding compositions, mentioning,inter alia, stearically hindered phenols as stabilizers.

[0033] DE-A 197 50 747 describes stabilizers for styrene co- andterpolymers, such as ABS, composed of a stearically hindered phenol, ofdilauryl and/or distearyl thiodipropionate, and of a phosphite.

[0034] None of the documents discloses impact-modifiedstyrene-acrylonitrile molding compositions which comprise all three ofthe additives D), E) and F), as described above, together, and where theweathered db* value of the molding compositions is below +5.0 after 100hours of exposure to light and weathering to ISO 4892/2, method A,black-panel temperature 65° C., using the CIE-Lab color system, to DIN6174 and DIN 5033.

[0035] A feature common to all of the prior art molding compositions isthat their stabilization with respect to weathering (rain, UV light) andheat-aging is unsatisfactory or is achieved only by sacrificing otheradvantageous properties, in particular by sacrificing their goodmechanical properties, such as toughness.

[0036] It is an object of the present invention to remove thesedisadvantages, and in particular to provide uncolored moldingcompositions which in particular when uncolored (i.e. without anyaddition of colorants which hide the intrinsic color of the moldingcompositions) have better weathering resistance and heat-agingresistance than the prior art molding compositions and which at the sametime have a balanced mechanical property profile, in particular hightoughness even after weathering and heat-aging. In addition, the moldingcompositions should have good flowability, and also good antistaticproperties. Compared with prior art molding compositions, the moldingcompositions should show less color change on weathering.

[0037] The molding compositions should also ensure that moldingsproduced from them have reduced tendency to form dust patterns when themoldings are stored in a dusty atmosphere. In addition, the moldingcompositions should have improved colorant dispersion, that is to saythat colorants, such as pigments, should be capable of particularlyuniform dispersion in the molding compositions. Finally, the moldingcompositions should have better demoldability when injection-molded.

[0038] We have found that this object is achieved by means of thethermoplastic molding compositions defined at the outset, and also byprocesses for their preparation, by their use, and by the resultantmoldings, fibers or films.

[0039] In the molding compositions of the invention, based in each caseon components A) to F),

[0040] the proportion of component A) is from 5 to 70% by weight,preferably from 8 to 65% by weight, and particularly preferably from 10to 60% by weight,

[0041] the proportion of component B) is from 29 to 90% by weight,preferably from 34 to 88% by weight, and particularly preferably from 39to 85% by weight,

[0042] the proportion of component C) is from 0 to 5% by weight,preferably from 0.01 to 5% by weight, and particularly preferably from0.01 to 4% by weight, in particular from 0.01 to 3% by weight,

[0043] the proportion of component D) is from 0.01 to 5% by weight,preferably from 0.03 to 4% by weight, and particularly preferably from0.05 to 3% by weight,

[0044] the proportion of component E) is from 0.01 to 5% by weight,preferably from 0.03 to 4% by weight, and particularly preferably from0.05 to 3% by weight,

[0045] the proportion of component F) is from 0.01 to 5% by weight,preferably from 0.02 to 4% by weight, and particularly preferably from0.1 to 3% by weight, and

[0046] the proportion of component G), based on components A) to G), isfrom 0 to 30% by weight, preferably from 0 to 25% by weight, andparticular preferably from 0 to 20% by weight.

[0047] The total of components A) to G) is, of course, 100% by weight.

[0048] Component A)

[0049] Component A) is a graft copolymer having an elastomericparticulate graft base a1) with a glass transition temperature below 0°C., measured by differential scanning calorimetry (DSC), as described inDIN 53765. This graft base may be selected from all of the knownsuitable elastomeric polymers. These are preferably diene rubbers,acrylate rubbers, EPDM rubbers, siloxane rubbers or other rubbers.

[0050] Component a1) is preferably at least one (co)polymer made from

[0051] a11) from 60 to 100% by weight, preferably from 70 to 100% byweight, of at least one conjugated diene or C₁-C₁₀ alkyl acrylate, or amixture of these,

[0052] a12) from 0 to 30% by weight, preferably from 0 to 25% by weight,of at least one other monoethylenically unsaturated monomer, and

[0053] a13) from 0 to 10% by weight, preferably from 0 to 6% by weight,of at least one crosslinking monomer.

[0054] Particularly suitable monomers a11) are butadiene, isoprene,chloroprene or mixtures of these, and also the C₁₋₁₀ alkyl acrylatesmentioned below, and mixtures of these. It is preferable to usebutadiene or isoprene or a mixture of these, especially butadiene, orelse n-butyl acrylate or 2-ethylhexyl acrylate, or a mixture of these,especially n-butyl acrylate. The use of butadiene is very particularlypreferred.

[0055] Where appropriate, monomers which vary the mechanical and thermalproperties of the graft base within a certain range may be present ascomponent a12). Examples which may be mentioned of thesemonoethylenically unsaturated comonomers are styrene, substitutedstyrenes, acrylonitrile, methacrylonitrile, acrylic acid, methacrylicacid, dicarboxylic acids, such as maleic acid and fumaric acid, and alsoanhydrides of these, such as maleic anhydride, nitrogen-functionalmonomers, such as dimethylaminoethyl acrylate, diethylaminoethylacrylate, vinylimidazol, vinylpyrrolidone, vinylcaprolactam,vinylcarbazol, vinylaniline, acrylamide, C₁₋₁₀-alkyl esters of acrylicacid, such as methyl acrylate, ethyl acrylate, n-propyl acrylate,isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butylacrylate, tert-butyl acrylate, ethylhexyl acrylate, the correspondingC₁₋₁₀ alkyl esters of methacrylic acid, and also hydroxyethyl acrylate,aromatic and araliphatic esters of acrylic acid or methacrylic acid,such as phenyl acrylate, phenyl methacrylate, benzyl acrylate, benzylmethacrylate, 2-phenylethyl acrylate, 2-phenylethyl methacrylate,2-phenoxyethyl acrylate, and 2-phenoxyethyl methacrylate, N-substitutedmaleimides, such as N-methyl-, N-phenyl-, and N-cyclohexylmaleimide,unsaturated ethers, such as vinyl methyl ether, and also mixtures ofthese.

[0056] Preferred components a12) are styrene, α-methylstyrene, n-butylacrylate, methyl methacrylate (MMA) and mixtures of these, in particularstyrene and n-butyl acrylate or a mixture of these, and especiallystyrene. If a component a12) is used, but no component a13), theproportion of component a11) is preferably from 70 to 99.9% by weight,particularly preferably from 90 to 99% by weight, and the proportion ofcomponent a12) is from 0.1 to 30% by weight, particularly preferablyfrom 1 to 10% by weight. Particular preference is given tobutadiene-styrene copolymers and n-butyl acrylate-styrene copolymerswithin the stated range of amounts.

[0057] Examples of crosslinking monomers of component a13) are divinylcompounds, such as divinylbenzene, diallyl compounds, such as diallylmaleate, allyl esters of acrylic or methacrylic acid,dihydrodicyclopentadienyl acrylate (DCPA), divinyl esters ofdicarboxylic acids, such as succinic acid or adipic acid, and diallyl ordivinyl ethers of dihydric alcohols, for example of ethylene glycol orof 1,4-butanediol.

[0058] The graft a2) is obtained from, based on a2),

[0059] a21) from 50 to 100% by weight, preferably from 55 to 90% byweight, and particularly preferably from 60 to 85% by weight, of atleast one styrene compound,

[0060] a22) from 0 to 50% by weight, preferably from 10 to 45% byweight, and particularly preferably from 15 to 40% by weight, ofacrylonitrile or methacrylonitrile, or a mixture of these, and

[0061] a23) from 0 to 50% by weight, preferably from 0 to 30% by weight,and particularly preferably from 0 to 10% by weight, of at least oneother monoethylenically unsaturated monomer.

[0062] The graft a2) contains at least one styrene compound a21).Preference is given to styrene, α-methyl styrene, or other substitutedstyrenes, and these styrenes may have one or more C₁-C₈-alkylsubstituents on the aromatic system. It is particularly preferable touse styrene or α-methyl styrene, or a mixture of these, veryparticularly preferably styrene.

[0063] Other monoethylenically unsaturated monomers a23) which may beused are those mentioned above as monomers a12), preferably methylmethacrylate (MMA) and n-butyl acrylate, particularly preferably MMA.

[0064] The graft a2) is preferably a styrene-acrylonitrile copolymer, inparticular having an acrylonitrile content of from 15 to 40% by weight.In one particular, likewise preferred, embodiment the graft a2) containsfrom 16 to 30% by weight, preferably from 17 to 28% by weight, inparticular from 18 to 25% by weight, of acrylonitrile.

[0065] The graft copolymers A) are usually prepared by emulsionpolymerization. The polymerization here generally takes place at from 20to 100° C., preferably at from 30 to 80° C. Conventional emulsifiers areoften added here, for example alkali metal alkyl- or alkylarylsulfonates, alkyl sulfates, fatty alcohol sulfonates, sulfosuccinates,ether sulfonates, resin soaps or salts of higher fatty acids having from10 to 30 carbon atoms. It is preferable to use the alkali metal salts,in particular the sodium or potassium salts of alkyl sulfonates, orfatty acids having from 10 to 18 carbon atoms. The emulsifiers aregenerally used in amounts of from 0.2 to 5% by weight, in particularfrom 0.3 to 3% by weight, based on the monomers used in preparing thegraft base.

[0066] In preparing the dispersion, it is preferable to use sufficientwater to give the finished dispersion a solids content of from 20 to 55%by weight. A water/monomer ratio of from 2:1 to 0.7:1 is usually used.

[0067] Suitable free-radical generators for initiating thepolymerization are those which decompose at the selected reactiontemperature, i.e. both those which decompose by themselves and thosewhich do so in the presence of a redox system. Examples of preferredpolymerization initiators are free-radical generators such as peroxides,preferably peroxosulfates (such as sodium or potassium peroxosulfate)and azo compounds, such as azodiisobutyronitrile. It is also possible,however, to use redox systems, especially those based on hydroperoxides,such as cumene hydroperoxide. The polymerization initiators aregenerally used in amounts of from 0.1 to 1% by weight, based on thegraft base monomers.

[0068] The free-radical generators and also the emulsifiers are added tothe reaction mixture, for example batchwise as a total amount at thebeginning of the reaction or in stages, divided into a number ofportions, at the beginning and at one or more later times, orcontinuously over a defined period. Continuous addition may also followa gradient, which may, for example, rise or fall and be linear orexponential or even a step function.

[0069] It is also possible to include in the reaction molecular weightregulators, such as ethylhexyl thioglycolate, n-dodecyl or t-dodecylmercaptan or other mercaptans, terpinols and dimeric methylstyrene orother compounds suitable for regulating molecular weight. The molecularweight regulators may be added to the reaction mixture batchwise orcontinuously, as described above for the free-radical generators andemulsifiers.

[0070] To maintain a constant pH, preferably from 6 to 9, buffersubstances may be added, for example sodium pyrophosphate,Na₂HPO₄/NaH₂PO₄, sodium hydrogen carbonate, or buffers based on citricacid/citrate. Molecular weight regulators and buffer substances are usedin conventional amounts, and no further details need therefore be givenin this connection.

[0071] It can also-be advantageous to use other electrolytes (inparticular salts) to adjust the particle sizes and their distribution.

[0072] In one particular embodiment, it is also possible to prepare thegraft base by polymerizing the monomers a1) in the presence of a finelydivided latex (the seed latex method of polymerization). This latex isthe initial charge and may be made from monomers which form elastomericpolymers or else from other monomers mentioned above. Suitable seedlatices are made from, for example, polybutadiene or polystyrene.

[0073] In another preferred embodiment, the graft base a1) may beprepared by the feed method. In this process, the polymerization isinitiated using a certain proportion of the monomers a1), and theremainder of the monomers a1) (the feed portion) is added as feed duringthe polymerization. The feed parameters (gradient shape, amount,duration, etc.) depend on the other polymerization conditions. Theprinciples of the descriptions given in connection with the method ofaddition of the free-radical initiator and/or emulsifier are once againrelevant here.

[0074] Graft polymers having a number of “soft” and “hard” shells arealso suitable.

[0075] The precise polymerization conditions, in particular the type,amount and method of addition of the emulsifier and of the otherpolymerization auxiliaries are preferably selected so that the resultantlatex of the graft polymer A) has a mean particle size, defined by thed₅₀ of the particle size distribution, of from 80 to 800 nm, preferablyfrom 80 to 600 nm and particularly preferably from 85 to 400 nm.

[0076] In one embodiment of the invention, the reaction conditions arebalanced in such a way as to give the polymer particles a bimodal orpolymodal particle size distribution, i.e. a size distribution with atleast two fairly pronounced maxima.

[0077] The bimodal particle size distribution is preferably achieved by(partial) agglomeration of the polymer particles. This can be achieved,for example, by the following procedure: the monomers, which form thecore, are polymerized to a conversion of usually at least 90%,preferably greater than 95%, based on the monomers used. This conversionis generally achieved in from 4 to 20 hours. The resultant rubber latexhas a mean particle size d₅₀ of not more than 200 nm and a narrowparticle size distribution (virtually monodisperse system).

[0078] In the second step, the rubber latex is agglomerated. This isgenerally done by adding a dispersion of an acrylate polymer. Preferenceis given to the use of dispersions of copolymers of C₁-C₄-alkylacrylates, preferably of ethyl acrylate, with from 0.1 to 10% by weightof monomers which form polar polymers, examples being acrylic acid,methacrylic acid, acrylamide, methacrylamide, N-methylol methacrylamideand N-vinylpyrrolidone. Particular preference is given to a copolymerfrom 90 to 96% of ethyl acrylate and from 4% to 10% of methacrylamide.The agglomerating dispersion may, if desired, also contain more than oneof the acrylate polymers mentioned.

[0079] In general, the concentration of the acrylate polymers in thedispersion used for agglomeration should be from 3 to 40% by weight. Forthe agglomeration, from 0.2 to 20 parts by weight, preferably from 1 to5 parts by weight, of the agglomerating dispersion are used for each 100parts of the rubber latex, the calculation in each case being based onsolids. The agglomeration is carried out by adding the agglomeratingdispersion to the rubber. The addition usually takes from 1 to 30minutes at from 20 to 90° C., preferably at from 30 to 75° C.

[0080] Besides an acrylate polymer dispersion, use may also be made ofother agglomerating agents, such as acetic anhydride, for agglomeratingthe rubber latex. Agglomeration by pressure or freezing is alsopossible. The methods mentioned are known to the person skilled in theart.

[0081] Under the conditions mentioned, the rubber particles are onlypartially agglomerated, giving a bimodal distribution. More than 50%,preferably from 60 to 95%, of the particles (distribution by number) aregenerally in the non-agglomerated state after the agglomeration. Theresultant partially agglomerated rubber latex is relatively stable, andit is therefore easy to store and transport it without coagulationoccurring.

[0082] To achieve a bimodal particle size distribution of the graftpolymer A), it is also possible to prepare, separately from one anotherin the usual manner, two different graft polymers A′) and A″) differingin their mean particle size, and to mix the graft polymers A′) and A″)in the desired mixing ratio.

[0083] The conditions for preparing the graft a2) may be the same asthose used for preparing the graft base a1), and the graft a2) may beprepared in one or more process steps. In two-stage grafting, forexample, it is possible to polymerize styrene and/or α-methylstyrenealone, and then styrene and acrylonitrile, in two sequential steps. Thistwo-step grafting (firstly styrene, then styrene/acrylonitrile) is apreferred embodiment. Further details concerning the preparation of thegraft polymers A) are given in DE-A 12 60 135 and 31 49 358 as well asEP-A 735 063.

[0084] It is advantageous in turn to carry out the graft polymerizationonto the graft base a1) in aqueous emulsion. It may be undertaken in thesame system used for polymerizing the graft base, and further emulsifierand initiator may be added. These need not be identical with theemulsifiers or initiators used for preparing the graft base a1). Forexample, it may be expedient to use a persulfate as initiator forpreparing the graft base a1) but a redox initiator system forpolymerizing the graft shell a2). Otherwise, that which was said for thepreparation of the graft base a1) is applicable to the selection ofemulsifier, initiator and polymerization auxiliaries. The monomermixture to be grafted on may be added to the reaction mixture all atonce, in portions in more than one step or, preferably, continuouslyduring a particular period of the polymerization.

[0085] If ungrafted polymers made from the monomers a2) are producedwith the graft base a1), these amounts, generally below 10% by weight ofa2), are counted with the weight of component A).

[0086] Component B)

[0087] Component B) is a hard copolymer made from, based on B),

[0088] b1) from 50 to 100% by weight, preferably from 55 to 90% byweight, and particularly preferably from 60 to 85% by weight, of atleast one styrene compound,

[0089] 2) from 0 to 50% by weight, preferably from 10 to 45% by weight,and particularly preferably from 15 to 40% by weight, of acrylonitrileor methacrylonitrile, or a mixture of these, and

[0090] b3) from 0 to 50% by weight, preferably from 0 to 30% by weight,and particularly preferably from 0 to 20% by weight, of at least oneother monoethylenically unsaturated monomer.

[0091] Component B) preferably has a viscosity number VN (determined toDIN 53726 at 25° C., 0.5% by weight in dimethylformamide) of from 50 to120 ml/g, particularly preferably from 52 to 110 ml/g, and in particularfrom 55 to 105 ml/g.

[0092] The styrene compound b1) used may be the monomers mentioned fora21), in particular styrene, α-methylstyrene or a mixture of these. In amixture of this type the proportion of α-methylstyrene is preferably upto 50% by weight, based on b1). It is particularly preferable to useonly styrene.

[0093] The other monoethylenically unsaturated monomers b3) used may bethe abovementioned monomers for a12), in particular MMA, and alsoN-alkyl- and N-arylmaleimides e.g. N-phenylmaleimide.

[0094] B) is particularly preferably a styrene-acrylonitrile copolymer.It is particularly preferable to use a styrene-acrylonitrile copolymerhaving from 15 to 40% by weight, in particular from 20 to 33% by weight,of acrylonitrile as component b2). The copolymer particularly preferablycontains from 22 to 31% by weight, especially from 23 to 29% by weight,of acrylonitrile.

[0095] Copolymers of this type are obtained in a known manner by bulk,solution, suspension, precipitation, or emulsion polymerization,preferably bulk or solution polymerization. Details of these processesare described, for example, in Kunststoffhandbuch, Ed. R. Vieweg and G.Daumiller, Vol. V “Polystyrol”, Carl Hanser-Verlag Munich 1969, pp 118et seq.

[0096] Preference is given to thermoplastic molding compositions inwhich component a11 is butadiene and component B) is astyrene-acrylonitrile copolymer having from 10 to 50% by weight,preferably from 22 to 33% by weight, and in particular from 23 to 29% byweight, of acrylonitrile.

[0097] Component C)

[0098] Component C) is an EO-PO-EO three-block copolymer (EO is ethyleneoxide, PO is propylene oxide). The average molecular weight {overscore(M)}_(n) of the central PO block is preferably from 2000 to 4000,particularly preferably from 2200 to 3800, in particular from 2300 to3500, very particularly preferably about 2300, about 2750, or about3250, in each case ±10%. The average proportion of the terminal EOblocks taken together is preferably from 3 to 28% by weight,particularly preferably from 8 to 24% by weight, in particular fromabout 8 to 14% by weight or from 18 to 24% by weight, based on C).

[0099] The three-block copolymers used of the formula X-Y-X may beprepared in a manner known per se (N. Schönfeldt, GrenzflächenaktiveEthylenoxid-Addukte, Wissenschaftliche Verlagsgesellschaft mbHStuttgart, 1976, pp. 53 et seq.) by polymerization in which a centralpolypropylene oxide block Y is first prepared and a block X made fromethylene oxide units is attached onto each of its two ends. Themolecular weights given above are generally the average molecularweights (number-average {overscore (M)}_(n), for example determined fromthe OH value to DIN 53240).

[0100] Preferred three-block copolymers and their preparation are alsodescribed in EP-A 125 801 and EP-A 018 591.

[0101] Component C) is commercially available, e.g. as Pluronic® (Fa.BASF)

[0102] Component D)

[0103] Component D) is a butylated reaction product of cresol withdicyclopentadiene and has the formula (I)(n≦10, preferably≦6)

[0104] Use is preferably made of the isomer of the formula (II)

[0105] having an average molecular weight of from 600 to 700.

[0106] It is available commercially, for example as Santowhite®ML(Monsanto), Lowinox®622 CP46 or Lowinox®CPL (Lowi/Great Lakes),Wingsty®L (Goodyear) or Ralox®LC (Raschig).

[0107] Component E)

[0108] Component E) is a thiocarboxylic ester. Preference is given toC₆-C₂₀ fatty esters of thiopropionic acid, particularly stearyl estersand lauryl esters. It is particularly preferable to use dilaurylthiodipropionate, distearyl thiodipropionate, or a mixture of these.

[0109] Dilauryl thiodipropionate is commercially available, e.g. asCyanox®LTDP (American Cyanamid), Hostanox®SE1 or SE3 (Clariant);Irganox®PS 800 (Ciba-Geigy), Lowinox®DLTDP (Lowi) or Sumilizer®TPLR(Sumitomo). Distearyl thiodipropionate is commercially available, e.g.as Cyanox®STDP (American Cyanamid), Hostanox®SE2 or SE4 (Clariant),Irganox®PS 802 (Ciba-Geigy), Lowinox®DSTDP (Lowi) and Sumilizer®TPS(Sumitomo). The other suitable sulfur-containing carboxylic esters arealso known and commercially available.

[0110] Component F)

[0111] Component F) is an alkali metal salt or alkaline earth metal saltof a C₆-C₂₀ carboxylic acid. Preference is given to salts of sodium andof potassium, and also of magnesium, of calcium and of zinc. Preferredcarboxylic esters are those of stearic acid, lauric acid, oleic acid, orpalmitic acid. It is particularly preferable to use calcium stearate,zinc stearate, magnesium stearate, potassium stearate or sodiumstearate, especially Mg stearate or K stearate.

[0112] These substances are known and are commercially availablechemicals.

[0113] In the case of all of the additives C) to F) it is, of course,also possible to use mixtures of various additives C′), C″) . . . toF′), F″) . . . , these falling within the definition of the respectiveadditive.

[0114] Component G)

[0115] Component G), use may be made of various conventional auxiliariesand fillers other than components C) to F). Examples of substances ofthis type are lubricants, mold-release agents, axes, pigments, dyes,flame retardants, antioxidants, stabilizers to protect from light,fibrous or pulverulent fillers, fibrous or pulverulent reinforcingagents, antistatics, and also other additives, and mixtures of these.

[0116] Examples of suitable lubricants and mold-release agents arestearic acids, stearyl alcohol, stearic esters, stearamides, and, alsosilicone oils, montan waxes, and those based on polyethylene orpolypropylene.

[0117] Examples of pigments are titanium dioxide, phthalocyanine,ultramarine blue, iron oxides and carbon black, and the entire class oforganic pigments.

[0118] For the purposes of the present invention, dyes are any of thedyes which can be used for the transparent, semitransparent ornon-transparent coloring of polymers, in particular those dyes which aresuitable for coloring-styrene copolymers. Dyes of this type are known tothe skilled worker.

[0119] Examples of flame retardants which may be used are thehalogen-containing or phosphorus-containing compounds known to theskilled worker, magnesium hydroxide, and also other commonly usedcompounds, and mixtures of these. Red phosphorus is also suitable.

[0120] Suitable antioxidants are in particular stearically hinderedmononuclear or polynuclear phenolic antioxidants, which may have varioussubstituents and also have bridging by substituents. These include bothmonomeric and oligomeric compounds, which may have been built up fromtwo or more phenolic building blocks. It is also possible to usehydroquinones or hydroquinone analogs or substituted compounds, or elseantioxidants based on tocopherols or on derivatives of these. It is alsopossible to use mixtures of various antioxidants. In principle, use maybe made of any compounds which are commercially available or aresuitable for styrene copolymers.

[0121] Together with the phenolic antioxidants mentioned above by way ofexample, concomitant use may be made of what are known as costabilizers,in particular phosphorus- or sulfur-containing costabilizers. Such P- orS-containing costabilizers are known to the skilled worker and availablecommercially.

[0122] Examples of suitable stabilizers to protect from light arevarious substituted resorcinols, salicylates, benzotriazoles,benzophenones, and HALS (hindered amine light stabilizers), for examplethose commercially available as Tinuvin®.

[0123] Examples of fibrous or pulverulent fillers are carbon fibers orglass fibers in the form of glass wovens, glass mats or glass silkrovings, chopped glass, glass beads, and also wollastonites,particularly preferably glass fibers. When glass fibers are used, thesemay have been provided with a size and with a coupling agent to improvecompatibility with the components of the blend. The glass fibersincorporated may either be in the form of chopped glass fibers or elsein the form of continuous strands (rovings).

[0124] Suitable particulate fillers are carbon black, amorphous silica,magnesium carbonate, chalk, powdered quartz, mica, bentonites, talc,feldspar or in particular calcium silicates, such as wollastonite orkaolin.

[0125] The amounts added to each of the additives are those which areusual, and it is therefore unnecessary to give any details in thisconnection.

[0126] Weathering Resistance

[0127] The thermoplastic molding compositions of the invention give adb* value of below +5.0 after 100 hours of exposure to light andweathering to ISO 4892/2, method A, black-panel temperature 65° C.,using the CIE-Lab color system, to DIN 6174 and DIN 5033. This meanshigh weathering resistance and good discoloration resistance. CIE standsfor Commission Internationale de l'Eclairage. The db* is preferablybelow +3.0.

[0128] It is preferable that the thermoplastic molding compositions givea dG value below +10.0 after 100 hours of exposure to light andweathering to ISO 4892/2, method A, black-panel temperature 65° C., thecolor being subsequently measured to DIN 5033 at an observation angle of10° in D65 daylight with evaluation to DIN 6167 (i.e. that the moldingcompositions have very high weathering resistance). The dG value isparticularly preferably below +5.0, in particular below +2.5.

[0129] If the molding compositions comprise component C), it isparticularly preferable that they give a db* value below +1.5 and a dGvalue below +2.5 after exposure to light and weathering as describedabove (i.e. have still better weathering resistance).

[0130] It will be understood that these data relate to the uncoloredmolding compositions (molding compositions not colored with colorants).

[0131] Color measurement by the CIE-Lab method is described in detail inDIN 6174 in combination with DIN 5033, Parts 1-9, for example. DIN 5033defines the color measurement method and DIN 6174 defines the evaluationof the measurement by the CIE Lab method. These standards areincorporated herein by way of reference. The skilled worker will findfurther information in H. Völz, Industrielle Farbprüfung, Verlag VCH,Weinheim 1990, pp 171 et seq. and A. Berger-Schunn, PraktischeFarbmessung, Verlag Muster-Schmidt, Göttingen 1991, pp. 93 et seq.

[0132] db* is the difference between two b* values. The two b* valuesare determined by the CIE-Lab method and subtracted from one another.db* is therefore the difference in the b* value from two measurements.The first b* value here is determined prior to exposure of the specimento light and weathering for 100 hours, and the second db* value isdetermined thereafter.

[0133] The relationship is: db*=b* after weathering−b* prior toweathering. If the db* is positive (preceded by a positive sign) theimplication is a shift in the perceived color in the yellow direction,i.e. toward a higher Yellowness Index of the specimen. If db* isnegative (preceded by a negative sign), the implication is a shift inthe perceived color in the blue direction.

[0134] dG is the change in the Yellowness Index, the Yellowness Indexbeing defined as$G = {\frac{{1.301 \cdot X} - {1.149 \cdot Z}}{Y} \cdot 100}$

[0135] where X, Y, and Z are the standard color values to DIN 5033. Thisformula applies to measurement to DIN 5033 using an observation angle of10° with D65 daylight, and evaluation to DIN 6167. G is calculated fromthe above equation. dG is the difference between two G values. The firstG value here is determined prior to exposure to light and weathering for100 hours, and the second dG value is determined thereafter. Therelationship is: dG=G after weathering−G prior to weathering.

[0136] Preparation of the Molding Compositions

[0137] The molding compositions are preferably prepared by separatelypreparing the individual components A), B), D), E) and F) and, whereappropriate, C) and G), and mixing the components.

[0138] The graft polymer A) is preferably prepared by emulsionpolymerization, as described above, giving an aqueous dispersion.

[0139] The resultant dispersion of the graft polymer A) may either bemixed directly with components B), D), E) and F), and, whereappropriate, C) and G), or it may first be worked up. The latterprocedure is one of the preferred embodiments.

[0140] The dispersion of the graft polymer A) is worked up in a mannerknown per se. The graft polymer A) is usually firstly precipitated fromthe dispersion, for example by adding salt solutions (such as calciumchloride, magnesium sulfate or alum) or acids (such as acetic acid,hydrochloric acid or sulfuric acid) which can bring about precipitation,or else by freezing (freeze coagulation). Precipitation using high shearforces, or shear precipitation, is also possible, the high shear forcesbeing produced, for example, by rotor/stator systems or by forcing thedispersion through a narrow slit. The aqueous phase may be removed in ausual manner, for example by screening, filtering, decanting orcentrifuging. This preliminary removal of the dispersion water usuallygives graft polymers A) which are moist with water and have a residualwater content of up to 60% by weight, based on A), where the residualwater may, for example, either adhere externally to the graft polymer orelse be enclosed within it.

[0141] After this, the graft polymer may, if required, be dried in aknown manner, for example by hot air or using a pneumatic dryer. It islikewise possible to work up the dispersion by spray drying.

[0142] In one preferred embodiment, the graft polymers A) and the othercomponents B) to G) are mixed in a mixing apparatus, producing asubstantially molten polymer mixture.

[0143] “Substantially molten” means that the polymer mixture maycontain, besides the predominant molten (softened) fraction, a certainproportion of solid constituents, for example unmelted fillers andreinforcing materials, such as glass fibers, metal flakes or evenunmelted pigments, dyes, etc. “Molten” means that the polymer mixtureflows at least to some extent, i.e. that it is softened at least to theextent of having plastic properties.

[0144] The mixing apparatuses used are those known to the skilledworker. It is possible, for example, to mix components A) to G) byextruding, kneading or roll-milling these together, components A) to G)having been isolated, if necessary, in advance from the solutionobtained during the polymerization or from the aqueous dispersion.

[0145] If one or more components are incorporated in the form of anaqueous dispersion or of an aqueous or non-aqueous solution, the wateror the solvent is removed from the mixing apparatus, preferably anextruder, via a devolatilizing unit.

[0146] Examples of mixing apparatuses for carrying out the novel processare discontinuously operating heated internal mixers with or withoutrams, continuously operating kneaders, such as continuous internalmixers, screw compounders having axially oscillating screws, Banburymixers, and also extruders, roll mills, mixing rolls where the rolls areheated and calenders.

[0147] Preference is given to using an extruder as mixing apparatus.Single- or twin-screw extruders, for example, are particularly suitablefor extruding the melt. A twin-screw extruder is preferred.

[0148] In some cases, the mechanical energy introduced by the mixingapparatus during the mixing process is sufficient to bring about meltingof the mixture, and therefore it is not necessary to heat the mixingapparatus. Otherwise, the mixing apparatus is generally heated. Thetemperature depends on the chemical and physical properties ofcomponents A) to G), and is to be selected so that a substantiallymolten polymer mixture is produced. However, the temperature should notbe excessive, otherwise thermal degradation of the polymer mixture mayoccur. However, it may also be that the mechanical energy introduced issufficiently great to require cooling of the mixing apparatus. Themixing apparatus is generally operated at from 150 to 300° C.,preferably from 180 to 300° C.

[0149] In one preferred embodiment, the graft polymer A) is mixed withthe polymer B) and with the other components C) if present, D), E), andF), and also, where appropriate, G) in an extruder, the dispersion ofthe graft polymer A) being metered directly into the extruder withoutprior removal of the water of the dispersion. The water is usuallyremoved over the length of the extruder via suitable venting systems.Examples of venting systems which may be used are vents provided withretaining screws (which prevent the emergence of the polymer mixture).

[0150] In another embodiment, likewise preferred, the graft polymer A)is mixed with the polymer B) and with the other components C) ifpresent, D), E), and F), and also, where appropriate, G) in an extruder,the graft polymer A) having been isolated in advance from the water ofthe dispersion, e.g. by screening, filtration, decanting orcentrifuging. This prior removal of the water of the dispersion givesmoist graft polymers A) with a residual water content of up to 60% byweight, based on A), and the residual water here may, for example,either adhere to the outer surface of the graft polymer or else beenclosed within it. The residual water present may then be removed asdescribed above as vapor via venting devices on the extruder.

[0151] In one particularly preferred embodiment, however, the residualwater in the extruder is not removed solely as vapor. Instead, some ofthe residual water is removed mechanically in the extruder and leavesthe extruder in the liquid phase. To this end, a pressure is built up inthe extruder by baffles, and this pressure forces the water out of thepolymer. It flows through dewatering apertures in the form of liquidwater. The polymer B) and components C) if present, D), E), and F), andalso, where appropriate, G) may also be fed to this same extruder sothat the finished molding composition is extruded as product of theprocess.

[0152] Further details on this process can be found in WO-A 98/13412,for example, which is expressly incorporated herein by way of reference.

[0153] However, it is also possible to begin by dewatering the graftpolymer A) as described immediately above, by removing the water underpressure in the extruder, and to mix the dewatered graft polymer withthe other components B) to G) in a second extruder, or in another mixingapparatus.

[0154] If an extruder is used for removing the water under pressure, oras mixing apparatus, the different sections of the extruder may, as isgenerally known, be individually heated or cooled, so as to set an idealtemperature profile along the screw axis. The skilled worker is alsofamiliar with the fact that the individual sections of the extruder cangenerally have different lengths.

[0155] The temperatures and lengths to be chosen for the individualsections in a particular case differ depending on the chemical andphysical properties of components A) to G) and their mixing ratios. Thisalso applies to the-screw rotation rate, which can vary over a widerange. Merely by way of example, extruder screw rotation rates in therange from 100 to 1200 rpm, preferably from 100 to 350 rpm may bementioned.

[0156] In one preferred embodiment, the substantially molten polymermixture prepared in the mixing apparatus from components A) to G) issubjected to rapid cooling.

[0157] The rapid cooling usually takes place by bringing thesubstantially molten polymer mixture (abbreviated to polymer melt below)into contact with a cold medium or with a cold surface.

[0158] The term “cold” here indicates a temperature sufficiently farbelow the temperature of the polymer melt to cool the polymer meltrapidly once contact has been established. The term “cold” thereforedoes not always mean cooled. For example, a polymer melt at 200° C. canbe subjected to rapid cooling by water which has been preheated to30-90° C., for example. The decisive factor is that the differencebetween the temperature of the polymer melt and that of the cold mediumor of the cold surface is sufficient for rapid cooling of the melt.

[0159] The term “rapid” means that within a period of from 10 sec,preferably up to 5 sec, and particularly preferably up to 3 sec, thepolymer melt is converted from the molten to the solid state and cooled.

[0160] It is preferable for the polymer melt to be rapidly cooled usinga cold medium. These media may be gases or liquids.

[0161] Examples which may be mentioned of gaseous cold media (termed“cooling gas” below) are cooled or uncooled air or, in particular in thecase of polymer melts susceptible to oxidation, gases such as carbondioxide, nitrogen or noble gases. The cooling gas used is preferably airor nitrogen. The cooling gas is generally blown onto the polymer melt asit emerges from the mixing apparatus.

[0162] Liquid cold media (termed “cooling liquid ” below) which may beused are organic or inorganic cooling liquids. Examples of suitableorganic cooling liquids are oils and other high-boiling organic liquidsubstances which do not interact either chemically or physically (forexample by swelling or salvation, etc.) with the polymer melt to becooled, i.e. are chemically and physically inert toward the polymermelt.

[0163] It is preferable to use inorganic cooling liquids, in particularaqueous solutions or water. Particular preference is given to water,which during its use may be. cooled (freezing point to roomtemperature), uncooled, or temperature-controlled (room temperature toboiling point).

[0164] The cooling liquid is generally sprayed onto the polymer melt asit emerges. As an alternative, the polymer melt emerges from the mixingapparatus and passes directly into a bath of the cooling liquid. It isalso possible for the cooling liquid to be in the form of a wide stream(flood) of liquid when it is supplied to the emerging polymer melt.

[0165] Spraying of the polymer melt with cooling liquid is particularlyadvantageous when using mixing apparatuses which produce films (forexample roll mills, mixing rolls or calenders). The polymer meltemerging in the form of sheeting solidifies to give a film as a resultof spraying with cooling liquid.

[0166] It is particularly preferable for the polymer melt to emerge fromthe mixing apparatus directly into a bath of the cooling liquid, andvery particularly preferably into a water bath.

[0167] It is also possible, and in some cases preferable, for thepolymer melt emerging from the mixing apparatus first to be subjected toonly slight cooling by being brought into contact with a cooling gas,e.g. by blowing temperature-controlled air or an inert gas, such asgaseous nitrogen, onto the melt. This results in solidification of onlythe outer surface of the melt, while the interior of the polymer remainsmolten. The actual rapid cooling then takes place by bringing the melt,the surface of which has already solidified, into contact with a coolingliquid, e.g. water, whereupon the interior of the melt also hardens.

[0168] For example, the strands of polymer melt emerging from the dyehead of the extruder can first be superficially solidified by blowingair onto the melt, and the strands can then be passed into a water bathwhere the actual rapid cooling takes place.

[0169] The polymer melt hardened by the rapid cooling can be furtherprocessed in a manner known to the skilled worker. The solidifiedpolymer is generally comminuted by milling, chopping, pelletizing orother processes.

[0170] In a particularly preferred embodiment, the rapid cooling and thecomminution are undertaken by the underwater granulation process. Inunderwater granulation, the polymer melt is discharged from the mixingapparatus via a die plate in which the holes (nozzles) are preferablyround and preferably arranged in the shape of a circle. The die plate islocated underwater (or immersed in another cooling liquid) or is sprayedwith water (or another cooling liquid), and this may be done under aninert gas. Immediately behind the die plate on its outer side there arecutting apparatuses, preferably rotating knives, which separate thepolymer as it is discharged. The polymer is therefore separated byrotating knives and rapidly cooled in water (or another cooling liquid),solidifying to give grains whose shapes are generally to some extentround and bead-like.

[0171] Arrangements of the holes having other than circular shape andshapes of the holes which are other than round are, however, commonlyfound in the die plate.

[0172] In another embodiment, a process termed underwater extrudategranulation is used. For this, the melt is discharged as extrudate froma die plate and is immediately wetted and rapidly cooled by much wateror cooling agent and is then introduced, via a sloping plane, into awaterbath or cooling-liquid bath, and is granulated after cooling.

[0173] In a very particularly preferred embodiment, an extruder is usedas mixing apparatus for components A) to G), with the underwatergranulation just described. The discharge orifice of the extruder inthis embodiment. is therefore a die plate located underwater (or sprayedwith water) and having cutting apparatuses, in particular rotatingknives.

[0174] One preferred preparation process therefore comprises

[0175] 1) preparing the graft copolymer A) by emulsion polymerization,

[0176] 2) mixing the graft copolymer A) with the hard copolymer B) andwith the other components C) if present, D), E), F) and G) if present,in a mixing apparatus, producing a substantially molten polymer mixture,and

[0177] 3) rapidly cooling the substantially molten polymer mixturewithin 10 sec.

[0178] Particular preference is. given to thermoplastic moldingcompositions comprising the components A), B), D), E), F), and, whereappropriate, C) and G) described above, and butadiene as conjugateddiene all), obtainable by

[0179] 1) preparing the graft polymers A) by emulsion polymerization,giving a moist polymer A) which comprises up to 60% by weight, based onA), of residual water,

[0180] 2) mixing the moist graft polymer A) with the other components B)to G) in an extruder, producing a substantially molten polymer mixture,where at least 30% by weight of the residual water from the moist graftpolymer A) is removed under pressure in the form of liquid water as aresult of pressure build-up in the extruder, and

[0181] 3) rapidly cooling the substantially molten polymer mixture,within a period of 10 sec, by underwater granulation.

[0182] In another particularly preferred embodiment, the additives C) toG) are added at various junctures within the preparation process. Forexample, one or more of components C) to G) may be added while the graftcopolymer A) is still in the form of the aqueous dispersion/emulsion(prior to, during or after the polymerization reaction of A)), and theother components are added at a later juncture, for example during themixing in the extruder or other mixing apparatuses.

[0183] In another particularly preferred embodiment, one or more, orall, of the additives C) to G) are divided into two or more portions andthese portions are added at various junctures within the preparationprocess. For example, one portion of components D) and E) can be addedwhile the graft copolymer A) is still in the form of the aqueousdispersion/emulsion (prior to, during or preferably after thepolymerization reaction of A)), and the addition of the remainingportion may be delayed until during the mixing of components A) to G) inthe extruder or other mixing apparatuses.

[0184] It is very particularly preferable to add a portion of componentD) and a portion of component E) to the dispersion/emulsion of the graftcopolymer A) and to add the remaining portion of D) and E) during themixing of components A) to G) in the extruder.

[0185] It is preferable for at least that portion of D) and E) which isadded to the graft copolymer dispersion to be in the form of an aqueousdispersion, that is to say that a dispersion of D) and E) (in the formof a mixture or of two separate dispersions) is added to the dispersionof A).

[0186] The proportion of component D) which is added while the graftcopolymer A) is still in the form of the aqueous dispersion/emulsion ispreferably from 20 to 100% by weight, based on the total amount of D).The corresponding proportion of component E) is preferably from 30 to100% by weight, based on the total amount of E).

[0187] Another preferred preparation process therefore comprises

[0188] 1) preparing the graft copolymer A) by emulsion polymerization,

[0189] 2) adding some or all of component D) and some or all ofcomponent E) to the aqueous dispersion or emulsion prior to, during orafter the polymerization reaction of A),

[0190] 3) adding any remaining amount of components D) and E) into amixing apparatus in which components A), B), C) if present, E), F) andG) if present, are mixed, producing a substantially molten polymermixture, and

[0191] 4) rapidly cooling the substantially molten polymer mixturewithin 10 sec.

[0192] Properties of the Molding Compositions:

[0193] The molding compositions of the invention have very goodresistance to weathering, together with a balanced profile of mechanicalproperties, in particular high toughness, even after weathering and,respectively, heat-aging. The good weathering resistance and,respectively, heat-aging resistance is therefore not achieved at theexpense of the mechanical properties. The molding compositions of theinvention show little change in shade after weathering and,respectively, heat-aging, and develop only slight dust-patterning industy environments. They have improved colorant dispersion, and alsoimproved demolding when injection-molded.

[0194] The molding compositions can be used to produce moldings, fibersor films of any type. The thermoplastic molding compositions of theinvention can be processed by the known methods of thermoplasticprocessing, e.g. by extrusion, injection molding, calendering, blowmolding, compression molding, or sintering.

[0195] The median particle size d given is the ponderal median particlesize as determined using an analytical ultracentrifuge and the method ofW. Scholtan and H. Lange, Kolloid-Z. und Z.-Polymere 250 (1972) pp 782to 796. The ultracentrifuge measurement gives the cumulative weightdistribution of particle diameter in a specimen. From this it ispossible to find the percentage by weight of particles whose diameter isthe same as or smaller than a particular size.

[0196] The d₁₀ value gives that particle diameter at which the diameterof 10% by weight of all of the particles is smaller and that of 90% byweight is larger. Conversely, the d₉₀ value is that at which thediameter of 90% by weight of all of the particles is smaller and that of10% by weight is larger than that diameter which corresponds to the d₉₀value. The ponderal median diameter d₅₀ and the volume-median particlediameter D₅₀ are those diameters at which the diameter of 50% by weightand, respectively, 50% by volume of all of the particles is larger andthat of 50% by weight and, respectively, 50% by volume is smaller. Thed₁₀, d₅₀ and d₉₀ values characterize the breadth Q of the particle sizedistribution, where Q=(d₉₀-d₁₀)/d₅₀. As Q reduces, the distributionbecomes narrower.

EXAMPLES

[0197] Constituents of the Molding Compositions:

[0198] Graft polymer A:

[0199] A1: A graft rubber was prepared and agglomerated using emulsionpolymerization, as described in DE-AS 24 27 960, column 6, line 15 tocolumn 7, line 25. The graft rubber was composed of 60 parts by weightof polybutadiene graft base and of 40 parts by weight ofstyrene-acrylonitrile copolymer graft, and had a median particle sized₅₀ of 176 nm. The graft contained 30% by weight of acrylonitrile.

[0200] A2: Graft rubber is described for A1, but median particle sized₅₀ 146 nm and acrylonitrile content of the graft 20% by weight.

[0201] Where appropriate, additives C) to G), in the form of theiraqueous dispersions, were added to the resultant graft rubber dispersion(see Table 2).

[0202] The graft rubber dispersion was coagulated using MgSO₄ solution(unlike in DE-AS 24 27 960). The coagulated rubber was removed from thewater of the dispersion by centrifuging, and washed with water. Thisgave a rubber with about 30% by weight of adhering or enclosed residualwater.

[0203] Hard copolymer B:

[0204] The polymers B were prepared by continuous solutionpolymerization as described in Kunststoff-Handbuch, Ed. R. Vieweg and G.Daumiller, Vol. V “Polystyrol”, Carl-Hanser-Verlag, Munich, 1969, pp122-124. Table 1 summarizes the compositions and properties. TABLE 1Component B1 B2 B3 B4 Styrene [% by weight] 65 76 65 75 Acrylonitrile [%by weight] 35 24 35 25 Viscosity number VN¹⁾ [ml/g] 60 64 80 81

[0205] Three-block copolymer C:

[0206] Pluronic® ethylene oxide-propylene oxide-ethylene oxidethree-block copolymer from BASF was used. The average molar mass{overscore (M)}_(n) (number average, determined from the OH value to DIN53240) of the central PO block was 2300 g/mol, and the proportion ofterminal EO blocks in the copolymer taken together was 10% by weight,based on the copolymer. The portion of PO was therefore 90% by weight,based on the copolymer.

[0207] Component D:

[0208] Wingstay®L from Goodyear was used, a butylated reaction productof p-cresol with dicyclopentadiene having the formula II as given in thedescription.

[0209] Component E:

[0210] Irganox®PS 800 from Ciba was used, dilauryl thiodipropionate.

[0211] Component F:

[0212] A commercially available quality of magnesium stearate was used.

[0213] Component G:

[0214] G1: Topanol® CA from ICI,1,1,3-tris(2′-methyl-4′-hydroxy-5′-tert-butylphenyl)butane

[0215] G2: Irgafos® 168 from Ciba,tris-(2,4-bis(1,1-dimethylethyl)phenyl) phosphite

[0216] G3: Lowinox® 44S36 from Lowi, a sulfur-containing phenolicstabilizer, 4,4′-thiobis(2-tert-butyl-5-methylphenol)

[0217] Preparation of the blends:

[0218] After isolation by centrifuging, the graft rubber A comprisingresidual water was very substantially freed from residual water. To thisend, the rubber was dewatered in a Werner and Pfleiderer ZSK 30 extruderat 250 rpm and 5 kg/h throughput at 50° C. The dewatering took place viarestricted-flow pressure zones of the extruder screws and via associatedwater-removal apertures through which the residual water removed underpressure was discharged from the extruder.

[0219] The resultant very substantially dewatered rubber was intimatelymixed with the other components B) to G), with evaporation of theresidual water, in a Werner and Pfleiderer ZSK 30 extruder at 250 rpmand 10 kg/h throughput at 250° C. The molding composition was extruded,and the polymer melt was subjected to rapid cooling by being passed intoa water bath whose temperature was about 40° C. The hardened moldingcomposition was pelletized.

[0220] Production and testing of moldings:

[0221] The pellets obtained were injection molded at 240° C. melttemperature and 60° C. mold temperature to give test specimens.

[0222] For the weathering tests, plaques of dimensions 60×60×2 mm wereproduced. The specimens were exposed to light and weathering for 100hours to ISO 4892/2, Method A, black-panel temperature 65° C. Colormeasurement using the CIE Lab method was then undertaken as described inDIN 6174 in combination with DIN 5033, Parts 1-9.

[0223] The db values and dG values given in Table 2 were calculated asfollows:

[0224] For the db* value, the b* value was determined prior to exposureto light and weathering and again thereafter. The relationship is:db*=b* after weathering−b* prior to weathering.

[0225] For the dG value, the Yellowness Index G was calculated from$G = {\frac{{1.301 \cdot X} - {1.149 \cdot Z}}{Y} \cdot 100}$

[0226] where X, Y, and Z are standard color values to DIN 5033.Measurements were taken at an observation angle of 10° in D65 daylightand evaluated to DIN 6167. The G value was determined prior to exposureto light and weathering and again thereafter. The relationship is: dG=Gafter weathering−G prior to weathering.

[0227] For the heat-aging, test specimens (tensile specimens) wereproduced to ISO 11403-3 (Part 3), FIG. 1 on page 5 (Details of the ISO294-2 small tensile specimen”) with the dimensions given in thatspecification. Heat-aging took place at 90° C. The test specimens weretested to ISO 11403-3, the fracture energy being measured in the tensiletest. The table below gives the change in fracture energy after 12 weeks(2016 hours) of storage at 90° C. in percent, based on the initial valueA, which was set at 100%. In order to exclude the effect of anyorientation or relaxation phenomena in the test specimen the initialvalue A was taken as the arithmetic average of measurements after 48,168 and 336 hours of heat-aging (2 days, 1 week and 2 weeks).

[0228] Table 2 gives the results. TABLE 2 Composition of the moldingcompositions (in parts by weight) and properties (C = for comparison, nd= not determined) Example 1 2 3 4 5 6 7 Graft copolymer A 43 43 29 29 2929 29 A1 A1 A2 A2 A2 A2 A2 Copolymer B 57 57 71 71 71 71 71 B1 B1 B2 B2B2 B2 B2 Three-block copolymer C ²⁾ — — — — — 0.5 — Wingstay ® L D ¹⁾0.4/ 0.2/ 0.2/ 0.2/ 0.2/ 0.2/ 0.6/ — — 0.1 0.15 0.1 0.15 — Dilaurylthiodipropionate E ¹⁾ 0,8/ 0.4/ 0.4/ 0.4/ 0.4/ 0.4/ 1.2/ — — 0.2 0.150.2 0,15 — Magnesium stearate F ²⁾ 0.25 0.25 0.25 0.25 0.25 0.25 0.25Other additives G ²⁾ — — — — 0,1 — — G2 db*³⁾ +0.2 −0.2 +2.3 +2.4 +1.8+1.1 +2.0 dG³⁾ +0.6 −0.6 +4.7 +4.9 +3.7 +2.2 +4.0 Change in the fractureenergy ⁴⁾ nd nd nd 72 60 55 76 [% of the initial value A] Example 8 C1C2 C3 C4 C5 C6 Graft copolymer A 29 30 43 29 40 29 44 A2 A1 A1 A2 A2 A2A1 Copolymer B 71 70 57 71 60 71 56 B2 B1 B3 B2 B4 B2 B1 Three-blockcopolymer C ²⁾ — — — — — — — Wingstay ® L D ¹⁾ 0.2/ —/ —/ —/ —/ —/ —/ —— — — — 0.25 — Dilauryl thiodipropionate E ¹⁾ 0.4/ —/ —/ —/ —/ —/ —/ 0.20.2 0.2 0.2 0.2 — — Magnesium stearate F ²⁾ 0.25 0.25 0.25 0.25 0.250.25 0.25 Other Additives G ²⁾ 0.1 0.2 0.2 0.2 0.2 0.2 0.2 G1 G3 + G3 +G3 + G3 + G3 G3 0.1 0.1 0.1 0.1 G1 G1 G1 G1 db* ³⁾ +1.8 +8.1 +7.3 +11.9+13.2 +10.2 +14.3 dG ³⁾ +3.9 +17.0 +15.1 +27.6 +28,7 +23.1 +29.0 Changein the fracture energy ⁴⁾ 54 8 10 15 8 53 nd [% of initial value A]

[0229] The table shows that only those molding compositions which,according to the invention, comprise all three additives D), E), and F)have a high weathering resistance (db*<+5.0, dG<+10.0). A particularlyhigh weathering resistance is displayed by molding compositions which(at a given rubber content of the molding composition of 29 parts byweight) further comprise the component c) (Example 7 with db*<+1.5 anddG<+2.5).

[0230] In contrast, molding compositions which, not according to theinvention, do not contain one or more of the three additives D), E), andF) display a considerably worse weathering resistance. Component D) isabsent in Examples C1 to C4, component E) is absent in Example C5 and D)and E) are absent in Example C6, as a result of which very high valuesof db* and dG are obtained in all cases: db*>+7, dG>15.

[0231] The table also shows that molding compositions in which, notaccording to the invention, one or more of the three additives D), E),and F) have been replaced by other additives (G1, G4) displaysignificantly worse weathering resistances than the molding compositionsof the invention.

[0232] Finally, it can be seen that only the molding compositions of theinvention still have good fracture energies after heat-aging for 12weeks. In the case of the molding compositions which are not accordingto the invention, the fracture energy drops sharply to as low as 8% ofthe initial value, while it remains at 54% or more of the initial valuein the case of the molding compositions of the invention. The thermalaging resistance of the molding compositions of the invention isaccordingly improved significantly.

We claim:
 1. A thermoplastic molding composition comprising, based oncomponents A) to F), A) from 5 to 70% by weight of at least one graftcopolymer A) made from, based on A), a1) from 10 to 90% by weight of atleast one elastomeric graft base with a glass transition temperaturebelow 0° C., and b2) from 10 to 90% by weight of at least one graft madefrom, based on a2), a21) from 50 to 100% by weight of at least onestyrene compound, a22) from 0 to 50% by weight of acrylonitrile ormethacrylonitrile, or a mixture of these, and a23) from 0 to 50% byweight of at least one other monoethylenically unsaturated monomer, B)from 29 to 90% by weight of a hard copolymer made from, based on B), b1)from 50 to 100% by weight of at least one styrene compound, b2) from 0to 50% by weight of acrylonitrile or methacrylonitrile, or a mixture ofthese, and b3) from 0 to 50% by weight of at least one othermonoethylenically unsaturated monomer, C) from 0 to 5% by weight of atleast one three-block copolymer X-Y-X having a central block Y made frompropylene oxide units and having terminal blocks X made from ethyleneoxide units, D) from 0.01 to 5% by weight of at least one butylatedreaction product of p-cresol with dicyclopentadiene of the formula (I)

 where n≦10, E) from 0.01 to 5% by weight of at least one thiocarboxylicester, F) from 0.01 to 5% by weight of at least one alkali metal salt oralkaline earth metal salt of a C₆-C₂₀ carboxylic acid, and G) from 0 to30% by weight, based on components A) to G), of other conventionaladditives, where the weathered db* value of the molding compositions isbelow +5.0 after 100 hours of exposure to light and weathering to ISO4892/2, method A, black-panel temperature 65° C., using the CIE-Labcolor system, to DIN 6174 and DIN
 5033. 2. A thermoplastic moldingcomposition as claimed in claim 1, where the molding composition has adG value below +10.0 after 100 hours of exposure to light and weatheringto ISO 4892/2, method A, black-panel temperature 65° C. the colormeasurement to DIN 5033 at an observation angle of 10° in D65 daylightwith evaluation to DIN
 6167. 3. A thermoplastic molding composition asclaimed in claim 1 or 2, in which the graft base a1) is a polymer madefrom, based on a1), a11)from 60 to 100% by weight of at least oneconjugated diene or C₁-C₁₀ alkyl acrylate, or a mixture of these,a12)from 0 to 30% by weight of at least one other monoethylenicallyunsaturated monomer, and a13)from 0 to 10% by weight of at least onecrosslinking monomer.
 4. A thermoplastic molding composition as claimedin claim 3, in which component a11) is butadiene and component B) is astyrene-acrylonitrile copolymer having from 10 to 50% by weight ofacrylonitrile.
 5. A thermoplastic molding composition as claimed inclaim 3 or 4, in which component a11) is butadiene and component B) is astyrene-acrylonitrile copolymer having from 22 to 33% by weight ofacrylonitrile.
 6. A thermoplastic molding composition as claimed in anyof claims 1 to 5, in which the proportion of component C) present isfrom 0.01 to 5% by weight.
 7. A thermoplastic molding composition asclaimed in claim 6, in which the propylene oxide central block Y ofcomponent C) has an average molecular weight {overscore (M)}_(N)(number-average) of from 2000 to
 4000. 8. A thermoplastic moldingcomposition as claimed in any of claims 1 to 7, in which component E) isdilauryl thiodipropionate or distearyl thiodipropionate, or a mixture ofthese.
 9. A thermoplastic molding composition as claimed in any ofclaims 1 to 8, in which component F) is potassium stearate or magnesiumstearate, or a mixture of these.
 10. A process for preparing thethermoplastic molding composition as claimed in any of claims 1 to 9,which comprises 1) preparing the graft copolymer A) by emulsionpolymerization, 2) mixing the graft copolymer A) with the hard copolymerB) and the other components C) if present, D), E), F) and G) if present,in a mixing apparatus, producing a substantially molten polymer mixture,and 3) rapidly cooling the substantially molten polymer mixture within10 sec.
 11. A process for preparing the thermoplastic moldingcomposition as claimed in any of claims 1 to 9, which comprises 1)preparing the graft copolymer A) by emulsion polymerization, 2) addingsome or all of component D) and some or all of component E) to theaqueous dispersion or emulsion prior to, during or after thepolymerization reaction of A), 3) adding any remaining amount ofcomponents D) and E) into a mixing apparatus in which components A), B),C) if present, E), F), and G) if present, are mixed, producing asubstantially molten polymer mixture, and 4) rapidly cooling thesubstantially molten polymer mixture within 10 sec.
 12. The use of athermoplastic molding composition as claimed in any of claims 1 to 9 forproducing moldings, fibers or films.
 13. A molding, a fiber or a filmmade from a thermoplastic molding composition as claimed in any ofclaims 1 to 9.